Effect of annealing on electrical, structural, and optical properties of sol-gel ITO thin films

Indium tin oxide (ITO) thin films (In/Sn = 90: 10) prepared by the sol-gel dip-coating process on glass substrates, followed by annealing in air in the temperature range 150-550 degrees C were studied. Overall the films structure, surface roughness, and electrical performances are improved, leading to electrical resistivity fifth order of magnitude larger than before annealing and a more compact and crystalline films, translated by a preferential orientation in the (I I I) direction. Besides that, the films are highly transparent in the visible range, where it shows an average transmittance of 92.3% after annealing to 550 degrees C. The allowed direct band gap at temperature range 150-550 degrees C was estimated to be 3.32-4.21 eV, increasing as the annealing temperature also increases. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim